1. Field of the Invention
This invention relates generally to electronic temperature controllers, and more particularly to electronic temperature controllers for operating a plurality of temperature dissipating mechanisms within an internal combustion engine system.
2. Description of the Prior Art
It is well known that internal combustion engines operate more efficiently when the operating temperature of the system is held constant. In gasoline powered automotive engines, for example, mechanical thermostatic devices are often employed within the engine coolant system to regulate the flow of coolant through the engine system radiator and to maintain a relatively constant engine temperature. In diesel engines, particularly heavy duty diesel engines for semi-tractors and the like, the need to maintain a constant engine temperature is even greater than with gasoline automotive engines. Diesel engines operate at peak efficiency within a comparatively narrow temperature range, and efficiency falls sharply as the engine temperature deviates from this temperature range. Moreover, the engine can be permanently damaged if the operating temperature exceeds a predefined upper limit.
In order to maintain a constant engine temperature, for peak efficiency, prior art internal combustion engine systems have employed a variety of different heat dissipating mechanisms, either singly or in combination with one another. In a diesel engine system for use in heavy duty commercial trucking applications, it is accepted practice to employ a circulating coolant system having a radiator disposed in the front of the vehicle for cooling the circulating coolant. A shutter or adjustable louver system is disposed in front of the radiator to regulate the forced air flow as the vehicle is moving. Also, it is not uncommon to provide an over temperature warning system and/or engine shut down system for preventing engine damage when excessive temperatures are reached.
In some of the prior art temperature controlling systems using several such heat dissipative mechanisms, each heat dissipative mechanism is actuated by a dedicated thermostatic device used only to control that one mechanism. Such systems are quite costly since a plurality of temperature sensors or thermostatic devices must be used. Another prior art temperature controlling system uses a single thermostatic device which provides a temperature signal for comparison against a plurality of predetermined set point temperatures. Each of a plurality of heat dissipating mechanisms is actuated at its own unique set point temperature. In this fashion, one temperature sensor or thermostatic device is capable of independently controlling a plurality of separate heat dissipating mechanisms. As an example of this latter temperature controlling system, reference may be had to U.S. Pat. No. 3,568,648 to Cass, entitled Water Temperature Control For Diesel Engines, issued Mar. 9, 1971.
One problem with all prior art temperature controlling systems, whether based on a plurality of temperature sensors or on a single temperature sensor, is the inability to anticipate the engine system's cooling needs and to adapt the cooling system's performance to best suit the anticipated needs.